Grouping is great, and super fun for the most part. However, many of us are in a different place in life at this point so solo is more practical. There is no right or wrong in it. As for me. I mostly play solo and join raids when I can (casual raider--not "raider" status).
This is one reason I usually roll a rogue so I kind of force myself to be more social in-game, aside from my usual friends and guildies I enjoy bullshitting with.
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Ultimately, you dictate how you will play, and how you will be perceived by others. Have fun, don't let the game become tedious and tiresome, don't be an asshole to others, and, most importantly, do not let a game interfere with your goals as a person.
Cheers!